This invention relates to internal mold release compositions and to polyahl compositions containing same, as well as a process for preparing polymers in the presence of internal mold release compositions.
Polyurethane and/or polyurea moldings are being increasingly used in the manufacture of automobiles, furniture and in-home construction. Molded polyurethanes and polyureas are especially important because they are light weight, resistant to moisture, weather, temperature extremes and aging. For example, molded polyurethane elastomers have become of special interest in the manufacture of force-reducing impact media such as safety impact bumpers for automobiles.
The demand for molded polyurethane articles requires that they be produced in the largest numbers in the shortest possible time. Polyurethane forming mixtures are imminently suited for mass production because the reactants are liquid and are quick reacting. However, the problem has existed in removing the molded polyurethane article from the mold. Heretofore, release of molded articles from molds in which they have been formed has been achieved by coating the surface of the mold cavity with an agent which facilitates the release of the article from the walls of the mold cavity. Procedures such as this are described in U.S. Pat. Nos. 3,964,530; 3,640,769; 3,624,190; 3,607,397 and 3,413,390. Such external mold releases have several disadvantages. For example, the external mold release tends to cling to the molded part upon release from the mold thereby requiring that the external mold release agent be reapplied almost each time the mold is used. In applying the external mold release, it is critical to uniformly coat the entire mold surface to prevent the molded part from sticking to the mold. The need to repeatedly treat the mold and the care required in such treatment, add substantially to the expense and time required to mold polyurethanes.
An additional problem is that residue from the external mold release builds up as the mold is repeatedly used. This build-up eventually covers and obscures details on the mold cavity surface desirably imparted to the molded article. If severe enough, this residue can cause a loss of critical part dimensions. Thus, the build-up must be periodically removed from the mold, resulting in additional system downtime. The use of too much of an external mold release can lead to attack on the polymers by solvents contained in the external mold release formulation.
Further, the use of sprayed on external mold release, especially those containing solvent, have related environmental safety and/or hygiene disadvantages.
The use of internal mold release agents for use in molding polyurethane articles has been disclosed in U.S. Pat. Nos. 3,726,952; 4,024,088; 4,098,731; 4,130,698; 4,111,861; 4,201,847 and 4,220,727.
Various problems have arisen with the use of such internal mold release agents. Many bleed or creep to the surface of the molded article, thereby interfering with the article's ability to be painted. Other internal mold release agents are incompatible with polyols used in forming the polyurethane. Many seriously reduce the activity of the catalysts used in the reaction mixture. In addition, many cause a reduction in the physical properties of the molded polyurethane.
More recently, in copending application Ser. No. 570,141, an internal mold release agent comprising a primary or secondary amine and a metal salt of certain acids has been disclosed. Although the internal mold release agent overcomes the problems associated with earlier mold release agents, it is often too reactive due to the presence of primary or secondary amines to be of optimum utility in certain polyurethane formulations.
Despite these difficulties, it is desirable to provide an internal mold release agent for polyurethane moldings. Such internal mold release agents substantially reduce the time and cost of preparing molded polyurethanes and similar polymers. It would be desirable, therefore, to provide a mold release agent which provides for increased mold release of polyurethane moldings from mold cavities, increases the ease in which the molded part is demolded, does not significantly adversely effect the catalytic reactivity, which minimally alters the physical properties of the molded polyurethane, and/or is not too reactive for optimum utility in polyurethane formulations.